The present application relates generally to an improved data processing apparatus and method and more specifically to mechanisms for recycling charge between power domains of integrated circuits.
Modern microprocessors comprise a wide variety of functional units that may function independently or together with other functional units and/or subsystems. Thus, a set of otherwise unrelated devices (functional units and/or subsystems) may share a same clock and/or power lines, thereby forming power domains. When a power domain is unused or not currently needed, the functional units and subsystems within the power domain continue to use power, which may be referred to as leakage power. One method to reduce leakage power is through power gating, where power domains that are unused or not needed are powered down, while the rest of the power domains within the microprocessor continue to function normally.
However, in order to power up these power domains after power down, the various functional units and subsystems of the power domain represent large capacitances that need to be charged before the functional units and other subsystems would be ready to be actively utilized. Further, any charge that exists in an active power domain may be lost after the power domain is once again power gated.